Even as an experiment, changing the valve stem seals can proove fruitful....>This can be accomplished without removing the heads and rates about a 4 on a>1 - 5 scale of difficulty.>

If the oil ring are worn, one would expect the compression rings to be in>the same shape. A cylinder leak test is not a be all/end all test without>other tests being done (aside from the fact that a cylinder leak test can>only suggest the condition of the compression rings). The puff of smoke on>start up is usually a good indicator of stem seal concerns.. the only sure>way of confirming this is to visually check. It is more than likely that>there are many more trouble free miles to be had from your car with a simple>repair.>